184b - Intermediary metabolism Flashcards
Which cells secrete GLP-1 and GIP?
What is the stimulus?
L cells in the jejunum
Secreted in response to feeding
How does glucose affect the secretion of glucagon?
Glucose inhibits glucagon secretion
How does the beta cell sense glucose?
Glucose enters islet cells via insulin-independent GLUT2 tranpsorter
- -> Glycolysis
- -> ATP generated
- -> Closes ATP-dependent K+ channel
- -> Depolarization
- -> Voltage-gated Ca2+ channels open
- -> Insulin release
Which cells secrete ghrelin?
What is the stimulus?
Gastric wall cells
Secreted during a fasting state; hunger signal
When your stomach GRRRrowls you secrete GhRRRelin
Describe the signaling pathway that is activated when glucagon binds to its receptor
Glucagon receptor is a GPCR
Gs -> cAMP -> PKA -> energy mobilization, glucogneogenesis
How does glucagon affect insulin release?
Glucagon stimulates insulin release
Kind of counter-intuitive: Glucagon’s main job is to mobilize energy
BUT, will also stimulate insulin release to prevet hyperglycemia when energy is mobilized
What kind of receptor is the leptin receptor?
What is the end result of receptor activation?
JAK-STAT
- Satiety signals to the hypothalamus (ventromedial nucleus)
Describe the signaling pathway that is activated when insulin binds to its receptor
Insulin receptor = tyrosine kinase
- Insulin binds
- Dimerization
- Phosphorylates downstream proteins
- PKC/PI3 kinase pathway = energy storage
- > Glycogen and FA storage, GLUT4 activation
- RAS/MAP kinase pathway = use energy to grow
- > Gene expression, cell growth/differentiation
What kind of receptor is the ghrelin receptor?
What is the end result of receptor activation?
GPCR
- Induces hunger (signals to lateral nucleus of the hypothalamus)
- Decreases energy expenditure
Levels of the following hormones are increased in fasting state
- Insulin, ghrelin
- GLP-1, glucagon
- Glucagon, leptin
- Glucagon, ghrelin
d. Glucagon, ghrelin
List 3 mechanisms that insulin uses to lower blood glucose
- Glucose uptake into myocytes and adipocytes
- Decreaed glycogen breakdown, increased glycogen formation
- Decreased glucagon production
In a fed state, the following hormones are increased:
- Insulin, ghrelin
- GLP-1, glucagon
- Insulin and leptin
- Glucagon and ghrelin
c. Insulin and leptin
How does growth hormone affect insulin secretion?
Growth hormone stimulates insulin secretion
(but also causes insulin resistance?)
Which hormones make beta cells more sensitive to rising glucose, therefore potentiating insulin release? (2)
GLP-1, GIP
- Still need rising glucose as a stimulus for insulin release, but threshold is lower
Which cells secrete glucagon?
Alpha-cells in the Islets of Langerhans
